Real-Time Volume Rendering of Medical Data for a Virtual Environment - - PowerPoint PPT Presentation

▶
real time volume rendering of medical data for a virtual
SMART_READER_LITE
LIVE PREVIEW

Real-Time Volume Rendering of Medical Data for a Virtual Environment - - PowerPoint PPT Presentation

Aug 28, 2023 110 likes •392 views

Real-Time Volume Rendering of Medical Data for a Virtual Environment Philippe Cattin Mathias Griessen and Benedikt Bitterli Motivation Thousands of years ago [Prof. Alt, Uni Basel] Some history New stone age (10000 B.C.) Middle age

slide-1
SLIDE 1

Real-Time Volume Rendering of Medical Data for a Virtual Environment

Philippe Cattin Mathias Griessen and Benedikt Bitterli

slide-2
SLIDE 2

Motivation

slide-3
SLIDE 3

Thousands of years ago

[Prof. Alt, Uni Basel]

slide-4
SLIDE 4

Some history

Middle age Today New stone age (10’000 B.C.)

slide-5
SLIDE 5

Why Laser?

slide-6
SLIDE 6

Functional cuts

slide-7
SLIDE 7

Bone cut with a saw

slide-8
SLIDE 8

Bone cut with our laser

slide-9
SLIDE 9

Why still spend hours/days to segment data sets?

slide-10
SLIDE 10

Solution?

slide-11
SLIDE 11

Volume Rendering Basics

slide-12
SLIDE 12

Volume Rendering: Why?

Pros

  • High quality images
  • No manual input

Cons

  • Computationally complex
  • In VR difficult
  • Difficult scene renderer to

embed polygonal objects

slide-13
SLIDE 13

Classes of Volume Rendering Algorithms

Ray casting method (Object order algorithms)

  • Basic ray-casting
  • Using octrees

Plane Composing (Image order algorithms)

  • Basic slicing with 2D textures
  • Shear-warp factorization
  • Translucent textures with image-

aligned 3D textures

slide-14
SLIDE 14

Basic Forward Ray-Casting

slide-15
SLIDE 15
  • Transparency
  • Color
  • Emissivity

Transferfunction

slide-16
SLIDE 16

Challenges

  • 1 Million Triangles
  • Is considered a big mesh
  • 1 Million Voxels
  • Is considered small (100x100x100)
  • Typical size 512x512x500
slide-17
SLIDE 17

Design Choices

  • Interpolation method
  • Trilinear
  • Sampling method
  • Less in the peripheri
  • Step size along the ray
  • Adaptive using distance map
  • Early stopping
slide-18
SLIDE 18

Difficult Cases

slide-19
SLIDE 19
  • Fluffy objects
  • Lots of air
slide-20
SLIDE 20

Distance Map

  • Precalculated on GPU
  • Size of map ¼ x ¼ x ¼
  • Closest pixel (according to the transferfunction) spherically
slide-21
SLIDE 21

Shadows

slide-22
SLIDE 22
slide-23
SLIDE 23

Occlusion map

  • Pre-calculated on GPU
  • Size of map 1/4x1/4x1/4
  • 32 different directions
  • Environmap either
  • Static HDR image
  • Dynamic lamp (Gaussian)
  • Time for each image on GPU [3ms]
  • Special case when volume is

rotated/scaled

slide-24
SLIDE 24

Fusion with Mesh Objects

slide-25
SLIDE 25
slide-26
SLIDE 26

Example Video

slide-27
SLIDE 27

Video

slide-28
SLIDE 28

Conclusion

  • Volume Rendering for VR is possible
  • Mainly thanks to
  • Modern GPU hardware
  • Modern VR glasses
  • Clever programming

Soon demo app: https://www.diffuse.ch